Answer:
c. Maintaining an upright posture
Step-by-step explanation:
"Isometric contraction" is all about increasing the tension in the muscles without shortening or lengthening the length of the muscles. There's also no movement.
Among the choices above, it is only "Maintaining an upright posture" that doesn't have movement; therefore, this employs the isometric contraction. This kind of contraction increases a person's strength. Another example of this contraction is holding a weight overhead.